"Flake is a selfish narcissist who would stop one of the few things he actually could do for his country-confirm responsible judges," Huckabee wrote. "His hate of @realDonaldTrump exceeds his sense of duty. His proposal is unconstitutional anyway."

"Good riddance!" Huckabee wrote of Flake, who is retiring in early January. "Go hide in an elevator!"

Flake is a selfish narcissist who would stop one of the few things he actually could do for his country-confirm responsible judges. His hate of @realDonaldTrump exceeds his sense of duty. His proposal is unconstitutional anyway. Good riddance! Go hide in an elevator! https://t.co/tvnGrESClQ

Mueller is reportedly close to wrapping up his investigation into alleged collusion between Moscow and Trump's 2016 presidential campaign, as well as Russian interference in that year's election.

Some lawmakers are concerned that Trump's recent appointment of Matthew Whitaker as acting attorney general might lead to to Mueller's dismissal. Flake and others have advocated for legislation that would codify protections for Mueller.